1. Field of the Invention
The present invention relates to an idling state stabilizing device for an engine that stabilizes an engine speed in an idling state.
2. Description of the Related Art
A power generating system employing an engine of a motorcycle uses a magnet type flywheel magneto generator coupled to the engine that generates electric power by rotating the flywheel magneto. The power generating system is designed to keep a predetermined low engine speed when the engine is in an idling state. A predetermined amount of torque is necessary to rotate the magneto. There may be some situations where the magneto cannot be steadily rotated when the engine speed decreases because the torque generated by the engine also decreases. Particularly, small motorcycle engines and other small engines are apt to have such problems. Conventionally, the engine idle speed is set to be high so as to provide sufficient torque to steadily rotate the magneto. Additionally, when a battery voltage exceeds a predetermined value, the battery and the generator are electrically disconnected from each other by a regulator to prevent electric power from being excessively supplied. However, under such a disconnected condition, the engine load does not change much because a short-circuit in the regulator continues to flow current from the generator.
Japanese Patent Publication No. 2003-269216A discloses a power generating system and a control method thereof in which a battery condition is detected in an idling state and an engine speed is increased in response to the battery condition. The system is controlled to increase the engine idle speed to prevent the battery power from being wholly discharged when the engine is in the idling state.
However, in both the conventional art discussed above and the system described in Japanese Patent Publication No. 2003-269216A, the engine speed is increased to maintain the power generated by the magneto. Consequently, the engine rotates uselessly in the idling state, which results in poor fuel economy. The increase of the engine speed results in additional noise generation, particularly in small engines, such as those used in motorcycles. It is undesirable to have noises generated in the idling state which have a magnitude similar to that in a normal running state.